In a roadside barrier having a guard rail held above and parallel to the ground by a plurality of breakaway posts, the end of the guard rail turned toward the oncoming traffic passing the rail creates a considerable hazard. When a vehicle collides with the rail at any location other than the end of the rail the posts snap off and the considerable kinetic energy of the vehicle is absorbed by the entire rail so as to slow down and gently stop the vehicle without ricoheting it back into the traffic.
When the end of the guard rail is merely allowed to project beyond the end post it is usually necessary to provide some protective arrangement such as shock-absorbing blocks or the like. This projecting end otherwise constitutes a considerable hazard for a motor vehicle striking it.
It has also been suggested to bend the guard rail down at its end and bury it in the ground. Although this prevents the rail from impaling a vehicle colliding with it, it has the extremely dangerous effect of prying the vehicle up and often flipping it over in its own traffic lane or in the opposite traffic lane. The vehicle merely rides up the bent-down end section until it is overturned or simply launched over the guard rail.